1. Field of the Invention
The invention relates to cutter blades for the production of gears and, more particularly, to cutter blades for the face hobbing of parallel depth spiral bevel and hypoid gears.
2. Summary of Related Art
Spiral bevel and hypoid gear pairs are conventionally produced utilizing either an intermittent index face milling method or a continuous indexing face hobbing method. While most gear set manufacturers currently use the face milling method, the face hobbing process has been recently adopted by some manufacturers, especially those manufacturing such gear sets for vehicular applications. In a face hobbing machine, a circular face hob type cutter carrying a plurality of cutter blades is utilized, and the cradle, work and cutter axes rotate in a timed relationship until the entire part is completed. During the cutting process, the work and cutter continuously rotate, with successive cutter blade groups engaging successive tooth slots as the gear or pinion member is being cut. Advantageously, the face hobbing method produces uniform depth teeth, and parts are produced from the solid in one operation. The face hobbing method also requires fewer production steps and less production time than the face milling method.
In general, producers of gears have found it beneficial to apply a relief or chamfer to the tip of the teeth of the gear member, the pinion member, or both members of the gear set to reduce the noise which typically results from the operation of the gear set. Nonetheless, such a tip relief is typically not provided on face hobbed spiral bevel or hypoid gear sets. Rather, after the teeth have been cut, the tips thereof have been merely rounded off by means of a separate operation. Where a tip relief has been provided, the relief has been produced in an operation separate from, and subsequent to, the tooth cutting operation. In either case, the additional production step is generally disadvantageous with regard to cost, quality control, and manufacturing flexibility.